After 21 years of wrangling over health threats, uncertain science and industry pressure, the U.S. Environmental Protection Agency on Friday released its assessment of dioxins defining how toxic they are.
By Marla Cone, Editor in Chief Environmental Health News
February 17, 2012
After 21 years of wrangling over health threats, uncertain science and industry pressure, the U.S. Environmental Protection Agency on Friday released its assessment of dioxins defining how toxic they are. A group of about 30 toxic compounds, including the infamous chemical in Agent Orange, dioxins are byproducts of combustion emitted by waste incinerators, chemical manufacturing plants, pulp mills, smelters and other facilities. They persist in the environment and build up in the food supply and in human bodies. Most people are exposed through fish, meat and other animal products.
Studies have linked dioxins to cancer, disrupted hormones, reproductive damage such as decreased fertility, neurological effects in children and adults, immune system changes and skin disorders.
The EPA broke the risk assessment into two parts; today’s release includes only the non-cancer effects of dioxins.
When a draft was unveiled in 2010, the EPA had set the daily level of exposure considered acceptable at 0.7 picograms of dioxins per kilogram of body weight. In response, industry groups criticized the EPA for setting this so-called “reference dose” too low, saying it would alarm consumers and drive costly regulations. The level set by the World Health Organization/United Nations in 2001 is about three times higher.
The guidelines are not enforceable standards. But they are critical to guiding many actions, such as cleanup of Superfund and other hazardous waste sites, industrial emission controls and dietary guidelines for fish.
The first assessment was completed in 1985, and since then the scientific evidence linking dioxins to a variety of human health threats has grown. But at the same time, many scientific uncertainties have remained, fueling the debate over what levels of dioxins are safe. EPA launched this reassessment in 1991.
Dioxins have been called the most toxic manmade chemicals, based on animal studies that show effects at extremely low doses – in the parts per trillion. One dioxin compound, known as TCDD, was used in Agent Orange, the herbicide sprayed by the U.S. military throughout much of Southeast Asia during the Vietnam War.
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